From 33f8fdcedb01680427328d710594facef7a0092c Mon Sep 17 00:00:00 2001
From: Tomasz Maciej Nowak <tmn505@gmail.com>
Date: Thu, 14 Jun 2018 14:40:26 +0200
Subject: [PATCH 2/2] arm64: dts: armada-3720-espressobin: set max link to gen1

Since the beginning there's been an issue with initializing the Atheros
based MiniPCIe wireless cards. Here's an example of kerenel log:

 OF: PCI: host bridge /soc/pcie@d0070000 ranges:
 OF: PCI:   MEM 0xe8000000..0xe8ffffff -> 0xe8000000
 OF: PCI:    IO 0xe9000000..0xe900ffff -> 0xe9000000
 advk-pcie d0070000.pcie: link up
 advk-pcie d0070000.pcie: PCI host bridge to bus 0000:00
 pci_bus 0000:00: root bus resource [bus 00-ff]
 pci_bus 0000:00: root bus resource [mem0xe8000000-0xe8ffffff]
 pci_bus 0000:00: root bus resource [io  0x0000-0xffff](bus address [0xe9000000-0xe900ffff])
 pci 0000:00:00.0: BAR 0: assigned [mem0xe8000000-0xe801ffff 64bit]
 pci 0000:00:00.0: BAR 6: assigned [mem0xe8020000-0xe802ffff pref]
 [...]
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x3c
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x44
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x4
 ath9k 0000:00:00.0: enabling device (0000 -> 0002)
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x3c
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0xc
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x4
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x40
 ath9k 0000:00:00.0: request_irq failed
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x4
 ath9k: probe of 0000:00:00.0 failed with error -22

The same happens for ath5k cards, while ath10k card didn't appear at
all (not detected):

 OF: PCI: host bridge /soc/pcie@d0070000 ranges:
 OF: PCI:   MEM 0xe8000000..0xe8ffffff -> 0xe8000000
 OF: PCI:    IO 0xe9000000..0xe900ffff -> 0xe9000000
 advk-pcie d0070000.pcie: link never came up
 advk-pcie d0070000.pcie: PCI host bridge to bus 0000:00
 pci_bus 0000:00: root bus resource [bus 00-ff]
 pci_bus 0000:00: root bus resource [mem0xe8000000-0xe8ffffff]
 pci_bus 0000:00: root bus resource [io  0x0000-0xffff](bus address [0xe9000000-0xe900ffff])
 advk-pcie d0070000.pcie: config read/write timed out

Following the issue on esppressobin.net forum [1] the workaround seems
to be limiting the speed of PCIe bridge to 1st generation. This fixed
the initialisation of all tested Atheros wireless cards.
The patch in the forum thread swaped registers which would limit speed
for all Armada 3700 based boards. The approach in this patch, in
conjunction with "PCI: aardvark: allow to specify link capability" patch
is less invasive, it only touches the affected board.

For the record, the iwlwifi and mt76 cards were not affected by this
issue.

1. http://espressobin.net/forums/topic/which-pcie-wlan-cards-are-supported

Signed-off-by: Tomasz Maciej Nowak <tmn505@gmail.com>
---
 arch/arm64/boot/dts/marvell/armada-3720-espressobin.dts | 2 ++
 1 file changed, 2 insertions(+)

--- a/arch/arm64/boot/dts/marvell/armada-3720-espressobin.dts
+++ b/arch/arm64/boot/dts/marvell/armada-3720-espressobin.dts
@@ -79,6 +79,8 @@
 /* J9 */
 &pcie0 {
 	status = "okay";
+
+	max-link-speed = <1>;
 };
 
 /* J6 */
